vrfy: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/vrfy - from package: vrfy

You may install the required package with command apt-get install {package}

Error in other languages:
vrfy: bevel nie gevind nie
vrfy: comandă negăsită
vrfy: comando não encontrado
vrfy: commande introuvable
vrfy: command not found
vrfy: käsku ei ole
vrfy: không tìm thấy lệnh
vrfy: komanda nerasta
vrfy: Kommando nicht gefunden.
vrfy: kommandot finns inte
vrfy: komut yok
vrfy: nie znaleziono polecenia
vrfy: níor aimsíodh an t-ordú
vrfy: no se encontró la orden
vrfy: no s'ha trobat l'ordre
vrfy: opdracht niet gevonden
vrfy: parancs nem található
vrfy: perintah tidak ditemukan
vrfy: príkaz nenájdený
vrfy: příkaz nenalezen
vrfy: команда не найдена
vrfy: командата не е открита
vrfy: 命令找不到
vrfy: コマンドが見つかりません